Water treatment process and apparatus

ABSTRACT

The present invention provides a physical water treatment (PWT) method and apparatus to treat liquid coolants. Electrodes ( 22, 24 ) are provided in a coolant stream ( 21 ), and an alternating voltage is applied across the electrodes ( 22, 24 ) to produce an electric field through the coolant. The alternating voltage creates an oscillating electric field in the coolant that promotes the collision of dissolved mineral ions. The ions collide to form seed particles that precipitate out of solution. Bulk precipitation of seed particles decreases the availability of ions in solution which can crystallize on heat transfer surfaces. The seed particles adhere to additional ions that separate out of solution and form larger particles that may be removed from the coolant stream ( 21 ) using a variety of treatment measures. In addition to precipitating mineral ions, the electric field may be applied to destroy bacteria, algae and microorganisms that accumulate in the coolant stream ( 21 ).

RELATED APPLICATIONS

[0001] This application claims priority from U.S. ProvisionalApplication No. 60/347,853, filed Oct. 23, 2001, the entire disclosureof which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to water treatment, and more specificallyto an apparatus and a process for minimizing mineral scaling andbacterial growth on equipment that stores and/or conveys water.

BACKGROUND OF THE INVENTION

[0003] Containers and conduits that store or transport liquids oftenaccumulate mineral deposits from minerals present in the liquid. Forexample, Ca⁺⁺ ions combine with HCO₃ ⁻ ions to form CaCO₃ particles.Mineral deposits form in liquids in a variety of ways. Some mineral ionscombine in the liquid stream and form particles that settle ontosurfaces in the form of a soft loose sludge. This is sometimes calledparticulate fouling. In other instances, ions come out of solution at aheat transfer surface and form hard crystalline deposits or scaling thatbinds to the heat transfer surface. This latter phenomenon is oftenreferred to as crystallization or precipitation fouling.

[0004] Scaling can create significant problems in heat exchangers andother equipment that have hot surfaces in contact with liquid. Thesolubility of mineral compounds in water, such as CaCO₃, decreases asthe water increases in temperature. This is sometimes referred to asinverse solubility. As a result, when water enters a heat exchanger andincreases in temperature, dissolved mineral ions in the water come outof solution at the heat transfer surface where the water is the hottest.The calcium ions adhere directly to the heat transfer surface as theyreact with HCO₃ ⁻ ions. In the case of calcium ions, the reaction is:

Ca⁺⁺+2HCO₃→CaCO₃+H₂CO₃→CaCO₃+H₂O+CO₂↑.

[0005] As the reaction of CaCO₃ occurs on the heat transfer surface, theCaCO₃ particles bind to the heat transfer surface to form scale.Excessive scaling can damage heat exchangers and reduce the rate of heattransfer through the heat transfer surface. In extreme cases, scalingwill permanently damage equipment.

[0006] Mineral deposits in fluid conduits and equipment require periodicremoval. Brush punching tools that have a coarse scrubbing surface areadequate to remove softer mineral deposits formed by particulatefouling. However, brush punching is not effective to remove scalingcaused by crystallization fouling, and additional cleaning measures mustbe used. For example, chemical cleaning with acid solutions is oftenused in conjunction with brush punching to remove hardened scale fromheat transfer surfaces. These techniques are time consuming and laborintensive, requiring the equipment to be shut down for significantperiods of time.

[0007] In the present state of the art, physical water treatment (PWT)methods are used to reduce scaling in heat transfer equipment. Thesemethods use a variety of mechanisms, including permanent magnets,solenoid-coils, pressure drop devices, and vortex flow devices. Althoughthese methods employ different technologies, they are all used topromote bulk precipitation of mineral particles at locations away fromheat transfer surfaces. This reduces the dissolved concentration ofmineral ions that enters the heat exchanger, reducing the potential forscale formation in the heat exchanger. In the case of calcium ions, PWTmethods enhance molecular attraction of Ca⁺⁺ with HCO₃ ⁻ ions toprecipitate CaCO₃ particles in water.

[0008] In PWT methods, the aim is to encourage the formation of softsludge through particulate fouling, and prevent hardened deposits formedby crystallization fouling. Mineral ions are precipitated out ofsolution away from heat transfer surfaces to form seed particles in thebulk liquid. This reduces the concentration of ions entering the heatexchanger, and thereby decreases the potential for scaling on the heattransfer surfaces. As seed particles enter the heat exchanger, theyattract additional mineral ions that come out of solution as the watertemperature increases. The seed particles combine with the ions to formrelatively large particles that can be easily removed from the liquidstream. Particles that settle out of the liquid form a soft sludgethrough particulate fouling. This sludge may be easily removed by punchbrushing, or by scouring in areas having a higher water velocity.

[0009] In many prior art PWT methods, an electrical field is employed toencourage the attraction of Ca⁺⁺ ions and HCO₃ ⁻ ions toward oneanother. One or more elements are placed on the exterior of a pipe orcontainer, out of contact with the water, to generate an indirectelectrical field in the water. Indirect electric fields have limitedeffectiveness in reducing scale, because they generally do not provide astrong enough electric field in the water to efficiently induce bulkprecipitation. For example, it is known to surround a water carryingconduit with a solenoid coil driven by an alternating polarity in asquare-wave current signal to induce a pulsating (reversing) electricfield within the water. The electric field in the water is governed byFaraday s Law. According to Faraday s law, the electric field E isdescribed by:

∫E·ds=−δ/δ∫B·dA

[0010] where E is an induced electric field vector, s is a line vectorin the electric field, B is a magnetic field strength vector, and A isthe cross sectional area of the solenoid coil. In this arrangement, aninduced electric field is produced within the water, but the fieldtypically has a limited electric field strength. When the solenoid isdriven by a square-wave voltage signal having a voltage of 12 volts, 5amperes peak, and a frequency of 500 Hz, the electric field strength isnot more than about 5 mV/cm.

[0011] Under Faraday s law, the strength of the induced electric fielddepends on the solenoid coil diameter. The electric field strengthinduced in the water generally decreases as the diameter of the pipeincreases. Therefore, to provide adequate field strength in largerpipes, larger solenoid coil diameters must be used, thereby increasingmaterial and energy costs.

[0012] The strength of the induced electric field is also dependent onthe frequency of the signal. Bulk precipitation generally becomes moreefficient with higher frequencies (i.e. frequencies greater than 3,000Hz). However, self-induction in the solenoid system increases withfrequency under Faraday s Law, negating any benefit gained from theincreased frequency. In practice, the frequency in the solenoid-coilsystem is limited to 500 to 3,000 Hz. Since it is not efficient to usehigh frequencies in large pipe applications (i.e., greater than 6 inchdiameter), solenoid-coil systems are not desirable. From the foregoing,it is apparent that existing PWT methods that utilize indirectelectrical fields for the reduction of scaling leave something to bedesired.

SUMMARY OF THE INVENTION

[0013] In accordance with a first aspect of the invention, a method fortreating a liquid to reduce scaling is provided. In the method, a firstand a second electrode are placed in direct contact with the liquid, andthe liquid flows between the first and second electrodes. A voltagedifference is applied between the first and second electrodes to form anelectrical field across the liquid stream. The voltage is varied tocreate an oscillating electrical field through the liquid. A square wavevoltage may be used to stimulate collision of dissolved mineral ions inthe liquid to precipitate the minerals into seed particles, which arecarried in the liquid stream and ultimately removed. An optional filtermay be added in the fluid line to remove the seed particles from theliquid stream. In addition, a chemical may be added to the liquid streamto enhance separation of mineral ions from solution. The applied voltagemay also be used to provide a high frequency electric field that isadequate to destroy bacteria, algae and microorganisms in the liquid.

[0014] In accordance with a second aspect of the present invention, acoolant system is provided that operates in accordance with the firstaspect of the invention described above. A coolant stream, such as acooling water stream used to cool condenser tubes in a heat exchangerunit, is passed through a conduit. A pair of opposing electrodes aremounted in the interior of the conduit and configured so that thecoolant stream passes between the electrodes. A power control unit isconnected to the electrodes and sends an electric signal to theelectrodes to generate an electric field across the coolant stream. Theconduit connects to a heat exchanger that may be located downstream fromthe electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The foregoing summary as well as the following description willbe better understood when read in conjunction with the drawing figuresin which:

[0016]FIG. 1 is a schematic diagram of a water treatment apparatus inaccordance with the present invention.

[0017]FIG. 2 is a schematic diagram of a water coolant system thatemploys a water treatment apparatus in accordance with the presentinvention.

[0018]FIG. 3 is a schematic top plan view of the water treatmentapparatus used in the water coolant system of FIG. 2.

[0019]FIG. 4 is a schematic top plan view of a first alternateembodiment of a water treatment apparatus in accordance with the presentinvention.

[0020]FIG. 5 is a schematic top plan view of a second alternateembodiment of a water treatment apparatus in accordance with the presentinvention.

[0021]FIG. 6 is a schematic diagram illustrating the mobility of mineralions in a coolant stream in the absence of an electric field.

[0022]FIG. 7 is a schematic diagram illustrating the mobility of mineralions in a coolant stream in the presence of an electric field applied inaccordance with the present invention.

[0023]FIG. 8 is a schematic diagram of a second embodiment of a watercoolant system according to the present invention which includes anin-line filter.

[0024]FIG. 9 is a schematic diagram of a third embodiment of a watercoolant system according to the present invention which includes aside-stream filter.

[0025]FIG. 10 is a flow diagram showing the steps of a method oftreating coolant water in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0026] Referring now to the drawings, and to FIG. 1 in particular, anapparatus for inducing an electric field is shown and designatedgenerally as 20. The apparatus 20 has a first electrode 22 and a secondelectrode 24. The first electrode 22 is connected by a wire to firstterminal 32 on a power source 30, and the second electrode 24 isconnected by a wire to a second terminal 34 on the power source. Theelectrodes 22,24 are spaced apart, and a voltage difference is appliedacross the electrodes to create an electric field. In FIG. 1, theelectric field is represented by the double-ended arrows labeled E. Theelectrodes are placed in direct contact with a coolant stream 21 flowingthrough a cooling system. In FIG. 1, water is used as the coolant 21.The electrodes are positioned to apply the electric field directlyacross the liquid stream. The apparatus 20 is operable to promote bulkprecipitation of mineral ions present in the liquid and reduce thepotential for scaling in cooling system components.

[0027] In contrast to other treatment techniques, the electrodes 22,24used in the apparatus 20 are in direct contact with the coolant 21,rather than affixed to the exterior of a pipe or vessel. As a result,the electric field is applied directly to the coolant stream. Theelectric field properties are not limited by pipe diameter and are notsubject to self-inductance under Faraday s law. Consequently, theelectrodes 22, 24 can produce a higher field strength and operate athigher frequencies to more efficiently precipitate mineral ions from thecoolant 21.

[0028] The present invention may be used with a variety of coolants andcoolant applications. For example, the present invention may be used totreat a coolant stream that removes heat from condenser tubes in achiller or air conditioning unit. The coolant is treated to precipitatemineral ions and reduce the potential for scaling on heat transfersurfaces in the condenser tubes. The present invention may also be usedwith a liquid coolant in any application where it is desirable tocontrol scaling on heat transfer surfaces. For purposes of thisdescription, the present invention will be described as it is used withcooling water that is recycled through a chiller or air conditioningunit to remove heat from condenser tubes.

[0029] Referring now to FIGS. 2-5, embodiments of the present inventionwill be described in greater detail. As shown in FIG. 2, the electrodes22, 24 are typically installed in a cooling water system 40 for achiller unit 44. Cooling water 21 is circulated through the condenserside of the chiller unit 44 to remove heat from condenser tubes. Theheated cooling water 21 is discharged from the chiller 44 and returnedto a cooling tower 41 where heat energy in the cooling water is allowedto dissipate. As the cooling water 21 dissipates heat, the cooling wateris collected in a sump 42.

[0030] The electrodes 22, 24 are submerged in and directly contact thecooling water 21 in the sump 42. The cooling water 21 exits the sump 42by gravity through a discharge outlet 46 and flows back to the chiller44. The electrodes 22,24 are positioned on opposite sides of the outlet46 so that the cooling water stream 21 passes between the electrodes asit exits the sump 42. The electrodes 22, 24 may be formed of anyappropriate material. Preferably, the electrodes 22, 24 are formed ofgraphite or other non-metal material and are insulated from the bottomof the sump 42.

[0031] Referring to FIG. 3, the electrodes 22, 24 are each shown ashaving a generally arcuate or semi-circular cross section. Theelectrodes 22, 24 are positioned symmetrically about the outlet 46. Theshape of the electrodes 22, 24 may be configured in a number of ways toapply an electric field across the cooling water as it is dischargedfrom the sump 42. As shown in FIG. 4, the electrodes 22, 24 have aplanar shape. One or more pairs of planar electrodes may be used todirect an electric field across the coolant stream. In FIG. 4, one pairof opposing electrodes 22, 24 is disposed adjacent to the sump outlet46. In FIG. 5, two pairs of electrodes 22, 28 and 24, 26 are disposedadjacent to the sump outlet 46. Regardless of the number and arrangementof electrodes used, the electrodes are preferably fixed in a stableposition in the sump 42. The electrodes may be stabilized by suspensionrods, brackets or other suitable supports.

[0032] Referring again to FIG. 2, the electrodes 22, 24 are connected topower source 30. The power source 30 is operable to apply a voltagedifference across the electrodes 22,24 to form an electric field acrossthe cooling water stream as it exits the sump 42. The voltage is appliedas an alternating wave and may be generated from an AC power source. Thevoltage may have one of a variety of wave patterns, such as a squarewave, trapezoidal wave, or sinusoidal wave. The polarity of theelectrodes 22, 24 is reversed at a controlled frequency to induce anelectric field in the coolant. Preferably, the polarity of theelectrodes 22, 24 is reversed at a frequency between 500 Hz and 100,000Hz. For example, a frequency greater than 1,000 Hz may be used for a 12Vsignal and an output current of between 5-10 amperes.

[0033] A major benefit of the present invention is that it provides ahigher electric field intensity in the coolant than other PWT methods.Since the electrodes are placed in the liquid stream rather than on theexterior of a pipe or tank, there is virtually no restriction on thefrequency or current that can be used. In addition, there is norestriction on pipe diameter. A field strength of 1 V/cm may be producedin a 6-inch diameter fluid conduit, which is 200 times greater than thefield strength associated with the solenoid-coil system. Since theelectric field is not subject to self-induction, the frequency can beincreased to 100,000 Hz or higher. Field strength may be increased up to10 V/cm if desired. Moreover, the applied electric potential is safe touse because it can be as low as 12 V.

[0034] Referring now to FIGS. 6 and 7, the effect of the electric fieldon mineral ions in the cooling water 21 will be described in moredetail. In the absence of an electric field, mineral ions in the coolingwater stream have freedom of motion in a three-dimensional space. FIG. 6illustrates the three-dimensional motion of mineral ions in a fluidconduit in the absence of an electric field. Positive and negative ionsare free to move radially with respect to the conduit, i.e. in a twodimensional plane represented by the X and Y axes in FIG. 6. The ionsare also free to move axially with respect to the conduit, i.e. in thedirection of the Z axis in FIG. 6. With this freedom of motion, and thesmall size of the dissolved ions, the statistical probability ofcollision between ions and bulk precipitation of minerals is relativelysmall.

[0035] Now referring to FIG. 7, the motion of mineral ions in thecooling water 21 is illustrated in the presence of an electric fielddirected orthogonally to the flow direction. When the electric field Eis applied to the cooling water stream 21, ions in the cooling water aresubject to the electromotive forces induced by the electric field. Theorthogonal forces limit movement of the ions to a two dimensional planerelative to the stream, as shown by the shaded cross-sectional area inFIG. 7. The electric field moves positively charged ions in onedirection and negatively charged ions in the opposite direction, so thatpositive and negative ions are driven toward one another. Since theelectric field limits movement of the ions to a single plane, theelectric field increases the statistical probability of collisionbetween ions and bulk precipitation of minerals. As a result, theelectric field promotes the collision of ions, such as Ca⁺⁺ and HCO₃ ⁻,thereby causing the ions to combine and form mineral or seed particlesthrough bulk precipitation. As discussed earlier, bulk precipitationdecreases the concentration of free ions in the cooling water that enterthe heat exchanger 44, thereby reducing the potential for scaling on theheat transfer surface. The seed particles that enter the heat exchangerattract mineral ions as the dissolved mineral ions come out of solution,further reducing the potential for scaling in the heat exchanger.

[0036] Referring now to FIGS. 2 and 7, the operation of the coolingwater system 40 will now be described. Cooling water 21 is collected inthe sump 42 and exits the sump through the outlet 46. Electric power issupplied to the electrodes 22,24 from the power source 30 and creates avoltage difference across the electrodes. The polarity of the electrodesare alternated to form an oscillating electric field through the coolingwater stream 21. As the cooling water stream 21 passes through theelectric field, mineral ions are taken out of solution and form seedparticles through bulk precipitation, as described earlier. The seedparticles are suspended in the cooling water stream 21 as it exits thesump 46 and travels to the chiller 44. The cooling water stream 21 maybe conveyed to the chiller 44 via a pump 48, as shown in FIG. 2.

[0037] Cooling water enters the condenser side of the chiller 44 andcontacts the refrigerant condenser tubes. As the cooling water 21contacts the hot condenser tubes, it absorbs heat, and the temperatureof the cooling water rises, causing mineral ions to come out ofsolution. The seed particles formed from bulk precipitation attract theions and progressively grow into larger particles. The heated coolingwater stream 21 and mineral particles are discharged from the chiller 44and conveyed to the cooling tower 41 where the heat energy isdissipated. The mineral particles in the cooling water 21 graduallysettle to the bottom of the sump 42 and form soft sludge. Periodically,the sludge is removed from the bottom of the sump through a drain 43 orother suitable clean out method.

[0038] In some instances, mineral particles may settle in other areas ofthe cooling system 40, including the heat transfer surfaces in thechiller 44. Since the settled mineral particles form a soft sludge, thesludge is easily removed by shear forces created by passing coolingwater.

[0039] Thus far, the electrodes 22, 24 have been shown and described atthe base of the sump. It should be understood, however, that electrodesmay be installed at any point in the coolant loop to apply an electricfield across the cooling water stream. For example, the electrodes 22,24 may be provided inside the coolant pipe upstream in relation to theheat exchanger 44. In addition, electrodes may be placed at multiplelocations within the coolant loop.

[0040] Mineral particles formed by bulk precipitation may be removed bysettling the particles in the sump, as described earlier. Alternatively,the mineral particles may be removed from the coolant stream by a filterinstalled in the coolant system 40. Referring now to FIG. 8, a filter 50is shown installed in the coolant return line between the chiller 44 andthe cooling tower 41. As mineral particles attach to mineral ions thatcome out of solution, the particles can reach sizes on the order of 5-10μm. The specific gravity of these particles can be three times heavierthan water. As a result, the particles can be removed easily using anyappropriate filter, such as a mechanical filter or sand filter.Preferably, the particles are filtered by a cyclone filter, which is notprone to clogging or plugging by CaCO₃ and other mineral deposits thataccumulate in the filter.

[0041] Alternatively, the filter 50 is installed in a side-stream loop52 extending from the cooling tower 41, as shown in FIG. 9. Aside-stream loop may be desired, for example, where larger pipediameters (greater than four inches) are used in the main coolant loop.A filtration pump 54 is installed in the side-stream loop 52 to drawcooling water and sludge from the sump 42 of the cooling tower 41. Thepump discharges the water and sludge through the filter 50 to removemineral particles from the water. The filtered water is returned to thesump 42, where it is reused in the cooling system 40.

[0042] It may be desirable to use the foregoing treatment method andapparatus with other treatment options to improve the quality of thecooling water and reduce harmful deposits on heat transfer equipment.For example, the present invention may include the addition of a polymersolution to the cooling water. Long chain water-soluble compounds, suchas polyethylene oxide (PEO) or polyacrylamide (PAM), may be added tocooling water with a high hardness, i.e. a high mineral content. Thesecompounds help bridge calcium ions together in hard water. By bridgingcalcium ions, the availability of calcium ions in solution is reduced,decreasing the potential for scaling at heat transfer surfaces.

[0043] Thus far, the present invention has been described as it is usedto reduce the occurrence of scaling in a cooling water system. Theapplication of an electric field can also be used to prevent growth ofbacteria, algae and other microorganisms present in a coolant stream.Uncontrolled growth of microorganisms, called biofouling, can degradethe performance of heat transfer equipment and potentially damage theequipment. Biofouling is effectively eliminated by applying an electricfield to the cooling water stream at a current and frequency adequate tokill the microorganisms. In many cases, this is the same operatingcurrent and frequency used to promote bulk precipitation of minerals, asdescribed above. Microorganisms may also be destroyed by the action ofsubmicron mineral particles, which are toxic to certain microorganisms.Electrodes may be placed at the sump outlet 46, and/or at locationswhere microorganism growth is most likely to occur. Destroyed biologicalmaterial can be removed from the cooling water using the same techniquesfor removing mineral particles.

[0044] Referring now to FIG. 10, a block flow diagram illustrates thepreferred method for using a PWT system in a cooling water system. Itwill be understood that the diagram represents just one possible PWTmethod. The order in which the steps appear is not intended to representthe only possible sequence of steps, and other steps may be added oromitted without deviating from the scope of the method according to theinvention.

[0045] In step 200 of the preferred method, electrodes are provided inthe cooling water. In step 300, an alternating voltage is applied acrossthe electrodes to produce an electric field in the water between them.The polarity of the voltage is varied at a high frequency to produce anoscillating electrical field. In step 400, the cooling water stream isconveyed through the electrodes. As the cooling water passes between theelectrodes, the oscillating electrical field stimulates the collision ofdissolved ions in the cooling water.

[0046] In step 500 of the preferred method, the electrical fieldfrequency is controlled to promote bulk precipitation of mineral ionsout of solution. Efficiency of bulk precipitation increases as frequencyis increased. The ions are precipitated into seed particles that aresuspended in the cooling water and carried through the system by thecooling water stream. In step 600, the cooling water and seed particlesare conveyed to a heat exchanger, such as a chiller unit. The coolingwater passes through the condenser tubes of the chiller where thecooling water absorbs heat from the condenser tubes. As the coolingwater increases in temperature, dissolved mineral ions come out solutionand bind with the seed particles through intermolecular attraction.

[0047] In step 700 of the preferred method, the heated coolant isdischarged from the chiller unit and conveyed to a cooling tower. Heatenergy in the cooling water is dissipated in the cooling tower. As thecooling water dissipates heat, larger mineral particles settle to thebottom of the sump in the cooling tower and form a soft sludge. In step800, the mineral particles and sludge are removed from the coolingwater. Sludge may be removed through a drain or clean-out port at thebottom of the sump. Alternatively, or in addition, cooling water may bepumped through a side-stream filter line to remove mineral particlesfrom the cooling water, as described earlier. Filtered cooling water isreturned to the sump. In step 900, cooling water is discharged from thesump. The cooling water is recirculated through the system, and steps400-900 are repeated.

[0048] The terms and expressions which have been employed are used asterms of description and not of limitation. There is no intention in theuse of such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof. It is recognized,therefore, that various modifications are possible within the scope andspirit of the invention. Accordingly, the invention incorporatesvariations that fall within the scope of the following claims.

I claim:
 1. A method for treating a stream of liquid, comprising thesteps of: A. providing a first electrode and a second electrode indirect contact with a liquid stream such that the liquid flows betweenthe first and second electrodes; B. applying an alternating voltagebetween the first and second electrodes to generate an electrical fieldacross the liquid stream that stimulates the collision of mineral ionspresent in the liquid, thereby forming a plurality of seed crystals fromthe colliding mineral ions in the liquid; C. transporting the seedcrystals through the liquid to precipitate mineral crystals fromadditional mineral ions in the liquid; and D. removing the mineralcrystals from the liquid.
 2. The method of claim 1, wherein the step ofproviding the first and second electrodes in direct contact with theliquid stream comprises the steps of mounting the electrodes to theinterior wall of a conduit carrying said liquid stream.
 3. The method ofclaim 1, wherein the step of providing the first and second electrodesin direct contact with the liquid stream comprises the step of mountingthe electrodes at a discharge outlet in a tank containing the liquid. 4.The method of claim 1, wherein the step of applying the alternatingvoltage across the electrodes comprises the step of applying a voltagehaving a pre-selected wave form across the electrodes.
 5. The method ofclaim 4, wherein the pre-selected wave form is selected from a groupconsisting of a square wave, a trapezoidal wave, and a sinusoidal wave.6. The method of claim 1, wherein the step of removing the mineralcrystals from the liquid comprises conveying the liquid through acyclone filter.
 7. The method of claim 1, wherein the step of applyingan alternating voltage comprises the step of controlling the frequencyof the voltage to stimulate formation of CaCO₃ and MgCO₃ crystals. 8.The method of claim 1, further comprising the step of adding a chemicaladditive to the liquid for promoting the precipitation of minerals fromthe liquid.
 9. A method for treating a stream of liquid to minimizedamage to equipment surfaces that contact the liquid, comprising thesteps of: A. placing a first electrode and a second electrode in directcontact with a liquid stream such that the liquid stream flows betweenthe first and second electrodes; and B. applying an alternating voltagebetween the first and second electrodes to generate an oscillatingelectrical field across the liquid stream, whereby mineral particles areprecipitated from the liquid stream as the stream passes through theelectric field.
 10. The method of claim 9, wherein the step of applyingthe alternating voltage between the electrodes comprises the step ofapplying a voltage having a pre-selected wave form across theelectrodes.
 11. The method of claim 10, wherein the pre-selected waveform is selected from a group consisting of a square wave, a trapezoidalwave, and a sinusoidal wave. 11-27 (canceled)
 28. The method of claim11, further comprising the step of passing the liquid stream through afilter after the mineral particles are precipitated to remove themineral particles from the liquid.
 29. The method of claim 28, whereinthe filter comprises a cyclone filter.
 30. The method of claim 9,wherein the step of applying an alternating voltage between theelectrodes comprises generating an electrical field having a magnitudeand a frequency sufficient to destroy bacteria, algae andmicroorganisms.
 31. The method of claim 9, wherein the step of applyingan alternating voltage between the first and second electrodes comprisesforming an electrical field in the liquid stream with a field strengthof at least 1 V/cm.
 32. The method of claim 9, wherein the step ofapplying an alternating voltage between the first and second electrodescomprises forming an electrical field in the liquid stream having afrequency of at least 3,000 Hz
 33. A method of reducing scale formationon the interior of a heat exchanger in a closed loop system containing astream of cooling water, said method comprising the steps of: A.providing a first and a second electrode in a closed loop cooling watersystem upstream from a heat exchanger such that the cooling water is indirect contact with and flows between the first and second electrodes;B. applying an alternating voltage between the first and secondelectrodes to generate an electrical field across the cooling waterstream that stimulates the collision of mineral ions in the coolingwater, thereby forming a plurality of seed crystals from the collidingions in the cooling water; C. transporting the cooling water stream andseed crystals into the heat exchanger to precipitate mineral ions thatcome out of solution in the heat exchanger; D. removing the mineralcrystals from the cooling water stream; and E. recycling the coolingwater stream back through the first and second electrodes.
 34. Themethod of claim 33, wherein the step of applying an alternating voltagebetween the electrodes comprises forming a voltage wave operable tostimulate collision of mineral ions in the cooling water and precipitatecrystals from said mineral ions.
 35. The method of claim 34, furthercomprising the step of passing the cooling water through a filter afterthe mineral crystals are formed to remove the mineral crystals from thecooling water.
 36. The method of claim 35, wherein the filter comprisesa cyclone filter.
 37. The method of claim 33, wherein the step ofapplying an alternating voltage between the electrodes comprisesgenerating an electrical field having a magnitude and a frequencysufficient to destroy bacteria, algae and microorganisms.
 38. The methodof claim 33, wherein the step of applying an alternating voltage betweenthe first and second electrodes comprises forming an electrical field inthe liquid stream with a field strength of at least 1 V/cm.
 39. Themethod of claim 33, wherein the step of applying an alternating voltagebetween the first and second electrodes comprises forming an electricalfield in the liquid stream having a frequency of at least 3,000 Hz. 40.A coolant system, comprising: A. a conduit containing a coolant stream;B. a pair of opposing electrodes mounted in the interior of the conduitand configured such that a coolant stream in the conduit passes betweenthe electrodes; C. a power control unit operable to convey electricpower from a power source to the electrodes to generate an alternatingelectric field across the coolant stream; and D. a heat exchangerconnected to the conduit for receiving the coolant stream from saidconduit, wherein, the electric field generated by the electrodes isoperable to stimulate collision of mineral ions in the coolant andprecipitate mineral ions out of solution, reducing the concentration ofmineral ions that crystallize on a surface in the heat exchanger. 41.The coolant system of claim 40, further comprising a filter disposed insaid conduit and configured to receive the coolant stream and removemineral crystals from the coolant stream.
 42. The coolant system ofclaim 41, wherein the filter comprises a cyclone filter.
 43. The coolantsystem of claim 40, wherein the heat exchanger is located in adownstream direction from the electrodes.
 44. The coolant system ofclaim 40, wherein the heat exchanger comprises a plurality of condensertubes in a chiller unit.